2021 Volume 49 Issue 6 Pages 325-
Terahertz frequency, i.e., 0.1 ~ 10 THz in frequency corresponds to the intermediate region between electronics and photonics. Recent development of intense terahertz pulse generation technique has opened a new avenue for investigating low-energy electromagnetic responses of condensed matter systems far away from thermal equilibrium. Here we present our recent studies of topological Dirac and Weyl semimetals using intense terahertz pulse and ultrafast time-resolved spectroscopy. A Dirac semimetal Cd3As2 hosts 3-dimensional massless electrons with high mobility, which shows efficient harmonic generation. A Weyl antiferromagnet Mn3Sn shows large anomalous Hall effect comparable to ferromagnets instead of vanishingly-small net magnetization, and therefore attracts growing attention as a candidate material for fast spintronic information processing. Remarkable functionalities of the novel materials at room temperature would contribute to the next-generation high-speed electronics and spintronics in terahertz frequency.
